Physical Analysis of White and Brick Red Eri Silk Fiber

Despite growing interest in Eri silk, limited research compares the properties of white and brick red varieties, particularly their optical, mechanical, and crystallinity behaviour. This study investigates the structural, optical, thermal, and surface properties of both varieties using X-ray diffraction (XRD), UV–vis analysis (UV–vis), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM). The Eri silk fibers were evaluated for weight loss percentage, functional groups, thermal stability, tensile strength, and amino acid composition. Both experienced around 10% weight loss after degumming. UV–vis analysis revealed an increase in optical band gap and decrease in Urbach energy after degumming, indicating improved structural order. XRD analysis showed crystallinity of 55% for degummed white and 50% for brick red Eri silk fiber. TGA demonstrated that undegummed white Eri silk exhibited 10% less mass loss than brick red, indicating higher thermal stability. SEM analysis showed white fibers with an average diameter of 19.34 µm, compared to 16.32 µm for brick red. White Eri silk fiber also demonstrated superior stretchability and flexibility in tensile strength tests. Amino acid profiling indicated a higher alanine content in white fiber. These findings enhance the understanding of physical properties of Eri silk’s varieties for potential applications in textiles and biomaterials.